In normal, or non-test, operation, a voltage regulator typically is used to provide a regulated voltage to core circuitry of an integrated circuit (IC). However, in order to accurately test the integrated circuit, the voltage regulator can be bypassed so as to allow an external power supply to power the core circuitry of the IC during test operation. This test operation typically is initiated via a test mode signal supplied to an external pin of the IC. A spurious event, such as an unintended assertion of the test mode signal during normal operation, could cause the improper bypass of the voltage regulator and thereby cause the IC to operate erratically, which is of particular concern in critical applications.
The use of the same reference symbols in different drawings indicates similar or identical items.